1. Field of the Invention
The present invention relates to, for example, a display apparatus configured to display an image on a hold-type display device such as a liquid crystal panel by causing a light emitting device to emit light. The present invention can be applied to a master monitor, a picture monitor, and the like for checking an image, which are required to, for example, display an input image without multiplying a frame frequency of the input image by a constant factor.
2. Description of the Related Art
Conventionally, display apparatuses using a liquid crystal panel and the like have had such a problem that displaying a moving video image results in occurrence of an image lag feeling hereinafter referred to as a motion blur. One commonly taken measure against it is to display an image while multiplying a frame frequency of 60 Hz or 50 Hz by a constant factor, and reduce a hold time to eliminate an influence of a motion blur due to the hold time.
Multiplying a frame frequency by a constant factor requires generation of an intermediate image to display an image in a new frame. However, there is such a problem that, if an original video image contains an image of a stripe pattern and the like, an error occurs in generation of the intermediate image, as a result of which a viewer feels as if the video image is interrupted.
On the other hand, reducing the hold time without changing a frame frequency of 60 Hz or 50 Hz to reduce a motion blur raises a problem of occurrence of a flicker, thereby disturbing visibility.
Particularly in master monitors and picture monitors used for checking a video image, the hold time is fixed to a value of about 50% as a ratio (a duty ratio) during one frame time. The fixed duty ratio leads to occurrence of a motion blur in a quickly moving portion depending on a video image, and occurrence of a flicker in a bright image, but viewers use them while bearing with such a disturbance.
Therefore, it is required to minimize occurrence of a motion blur and a flicker without changing a frame frequency of 60 Hz or 50 Hz.
For example, as discussed in Japanese Laid-Open Patent Application Nos. 2011-22462 and 2011-13558, there is a technique for detecting a motion vector and controlling a hold time according to the detected motion vector.
Further, as discussed in Japanese Laid-Open Patent Application Nos. 2011-13558 and 2009-122552, there is a technique for controlling a hold time according to an image quality mode and a genre of a content.
Further, as discussed in Japanese Laid-Open Patent Application No. 2009-251069, there is a technique for controlling a hold time according to a luminance level of a partial region in a display, which enables reduction in occurrence of a flicker.
However, controlling the hold time according to the motion vector has such a problem that a flicker suddenly occurs at the moment that an object moves in a bright image. Further, the method for controlling the hold time according to the image quality mode and the genre of the content has such a problem that the method cannot be used for the master monitors, the picture monitors, and the like, on which image qualities of all contents need to be checked under a fixed mode. Further, the above-described conventional techniques share such a problem in common that a change in the hold time results in a change in a luminance, and the luminance change is corrected by applying a gain to a video image to maintain a constant luminance, which leads to an adverse influence on the image quality.
For example, the master monitors, the picture monitors, and the like are set in such a manner that a gamma curve has a continuous rise from a base luminance when a black signal is inserted. Further, the master monitors, the picture monitors, and the like are provided with some measure for facilitating an image quality check in a low gradation portion, such as linearization of a gamma curve in the low gradation portion. Therefore, a change in the gain for a video image during the video image causes a change in the luminance in the low gradation portion in the middle of the video image, disturbing a delicate work of the image quality check. Further, the change in the gain also causes a change in a peak luminance, providing different visibility of a high gradation portion in the video image. Therefore, normally, for the master monitors, the picture monitors, and the like, a fixed value is used as the gain without changing it.